Analog baseband interface for communication systems

ABSTRACT

A communication system interface between a baseband unit and a radio frequency (RF) unit is configured to advantageously use a common set of lines to carry both transmit and receive baseband analog signals between the baseband and RF unit, thereby enabling a relatively lower signal count and permitting loopback testing of elements within the baseband and the RF units.

RELATED APPLICATIONS

This application claims priority of U.S. Provisional Patent Application60/896,249, entitled “Analog Baseband Interface For CommunicationSystems” filed Mar. 21, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments described in this specification relate generally tocommunications systems and more particularly to an analog basebandinterface between wireless communication units.

2. Description of the Related Art

Wireless communications systems generally use radio frequency (RF)signals to transmit data from a transmitter to one or more receivers.Wireless communication systems are frequently used to implement wirelesslocal area networks (LANs) in which data is transmitted and receivedbetween computers, servers, Ethernet switches, hubs, and the like. Awireless LAN may, for example, allow web page data to be transferredbetween a server and a computer.

Many wireless communication systems may be divided into two or moreunits. A typical division occurs between an RF unit and a baseband unit.The RF unit may convert transmit baseband analog signals into RF signalsthat may be transmitted through an antenna. The RF unit may also receivean RF signal from an antenna and convert the RF signal to a receivebaseband analog signal. The baseband unit, working in conjunction withthe RF unit, may create the transmit baseband analog signal the RF unitprocesses and transmits and may also receive a receive baseband analogsignal from the RF unit that has been generated from a received RFsignal.

The baseband unit is typically coupled to other units within thewireless communication system. Other typical elements of wirelesscommunication systems may include elements configured to process data tobe transmitted. For example, data may need to be encoded by an encodingelement before the data can be processed by the baseband unit and thencoupled to the RF unit for transmission. Still other typical elements ofa wireless communication system may also include one or more digitalsignal processing units that can further process the data generated bythe baseband unit from the analog signal received from the RF unit.

FIG. 1 illustrates an exemplary prior art wireless communication system100 including a baseband unit 101 and an RF unit 111. Baseband unit 101includes a digital to analog converter (DAC) 102 and an analog todigital converter (ADC) 103, whereas RF unit 111 includes a transmitter(TX) 112 and a receiver (RX) 113. One or more antennas 110 may becoupled to RF unit 111. In many cases, RX 113 and TX 112 may shareantenna 110 (shown).

TX 112 of RF unit 111 is coupled via lines to DAC 102 in baseband unit101. Many wireless communication systems are configured to transmit morethan one RF signal contemporaneously. For example, two quadrature RFsignals are usually transmitted to support orthogonal frequency-divisionmultiplexing (OFDM) defined by wireless communication standards IEEE802.11a or 802.11g. Therefore, TX 112 is usually configured to accepttwo transmit baseband analog signals. The two transmit baseband analogsignals are also often relatively high bandwidth signals in order tosupport relatively high data transfer rates.

Differential line pairs are often used for high bandwidth signals inorder to increase, among other things, noise immunity and performance.One embodiment of a differential line pair encodes a signal with apositive component and a negative component. These two components aretypically implemented with two lines, each line carrying one component.

Oftentimes, the coupling between DAC 102 and TX 112 is through twodifferential line pairs. FIG. 1 shows two differential line pairs 107(i.e. I+, I−, Q+, and Q−) from DAC 102 in baseband unit 101 to TX 112 inRF unit 111. RX 113 receives an RF signal through antenna 110 andrecovers one or more receive baseband analog signals. As shown in FIG.1, two differential line pairs also couple RX 113 to ADC 103 in basebandunit 101, thereby facilitating the contemporaneous receipt of tworeceive baseband analog signals (for the same reason as described abovein the transmit case). Thus, wireless communication system 100 includesfour differential line pairs coupling baseband unit 101 and RF unit 111(i.e. eight discrete lines in total).

Multiple-input multiple-output (MIMO) wireless LAN architectures mayprovide improved performance when compared to single-input single-outputarchitectures. The improved performance may be provided by, in part,using a plurality of transmitters and receivers (transceivers) toprocess RF signals. FIG. 2 illustrates a portion of an exemplarymultiple transceiver wireless communication system 200, which can becharacterized as an extension of the system configuration of FIG. 1 (butis not known to be implemented or discussed in the prior art). System200, like system 100 (FIG. 1), includes a baseband unit 201 and an RFunit 211. However, in system 200, baseband unit 201 and RF unit 211 aredivided into three sub-units, i.e. A, B, and C (indicated by the suffixof each reference number). Note that in other embodiments, baseband unit201 and RF unit 211 may be divided into two sub-units or more than threesub-units.

A first baseband sub-unit 201A includes a first DAC 202A and a first ADC203A, a second baseband sub-unit 201B includes a second DAC 202B and asecond ADC 203B, and a third baseband sub-unit 201C includes a third DAC202C and a third ADC 203C. A first RF sub-unit 211A includes a firsttransmitter (TX) 212A and a first receiver (RX) 213A, a second RFsub-unit 211B includes a second TX 212B and a second RX 213B, and athird RF sub-unit 211C includes a third TX 212C and a third RX 213C.

System 200, like system 100, uses differential line pairs to couple theelements in baseband unit 201 to the elements in RF unit 211. In system200, two differential line pairs couple the DACs to the TXs and twodifferential line pairs couple the RXs to the ADCs. Therefore, to couplebaseband unit 201 to RF unit 211, twenty-four discrete, inter-unit lines(i.e. lines between baseband unit 201 and RF unit 211) are required.

Note that wireless communication system 200 may be configured to enableloopback testing. Loopback testing is a testing method that allows auser to test or calibrate portions of a wireless communication systemwithout the need to transmit or receive data to or from a secondwireless communication system. Loopback testing, therefore,advantageously makes possible some amount of testing or calibration ofthe wireless communication system without relying on a separate wirelesscommunication system.

Typically, during loopback testing, data passes through a loopbackprocessing chain of elements that includes a DAC, a TX, a RX, and anADC. Oftentimes, the loopback processing chain is configured such thatthe DAC is coupled to the TX that is coupled to the RX that is furthercoupled to the ADC. All the elements within the loopback processingchain may function contemporaneously to process test data. Specifically,the test data is often introduced into the loopback processing chain atthe DAC, proceeds from the DAC to the TX, continues from the TX to theRX and finally travels to the ADC. The testing and calibration may comeabout by understanding the test data that is introduced to the loopbackprocessing chain and examining the data that is returned from theloopback processing chain.

For example, using system 200 to test sub-unit A in loopback fashion,test data would be introduced to DAC 202A; DAC 202A would send data toTX 212A. The output of TX 212A would be sent to RX 213A. The output ofRX 213A would then be sent to ADC 203A. The data from ADC 203A wouldthen be examined. Thus, when wireless communication system 200 isconfigured in this fashion, the elements within the loopback processingchain may function contemporaneously, and one or more of the elementswithin the first baseband sub-unit 201A (i.e. DAC 202A and 203A) and thefirst RF sub-unit 211A (i.e. TX 212A and RX 213A) may be tested orcalibrated.

One drawback to the architecture of system 200 is the relatively highinter-unit line count between baseband unit 201 and RF unit 211.Specifically, consider a typical implementation of wirelesscommunication system 200 in which baseband unit 201 and RF unit 211 areon separate integrated circuits (ICs). In this implementation, each linecoupling baseband unit 201 to RF unit 211 may require two pins, i.e.each IC may require one pin to connect to each line. Thus, eachdifferential line pair may require four pins, i.e. each IC may requiretwo pins to connect to each differential line pair. As a result, thetwelve differential line pairs coupling baseband unit 201 and RF unit211 may require twenty-four pins on each IC or forty-eight pins intotal. As is well-known, relatively greater amounts of pins cansignificantly and undesirably increase the cost of an IC package.

Another drawback is that relatively large numbers of high-speed,differential line pairs, particularly differential traces used to couplebaseband unit 201 and RF unit 211, may be relatively difficult todesign. Specifically, differential traces may have relatively morestringent design rules than other, low speed traces. As is well-known,more stringent design rules generally require more design effort thanless stringent design rules, such as those that may be required for lowspeed traces. Therefore, more differential lines pairs generallyincrease the design effort required to a design wireless communicationsystem.

Therefore, a need arises to reduce the number of lines between basebandand RF units in a wireless communication system while still retainingthe advantages of loopback testing.

SUMMARY OF THE INVENTION

A wireless communication system that advantageously reduces the numberof lines between baseband and RF units is provided. This wirelesscommunication system can include a baseband unit, an RF unit, and aplurality of sets of inter-unit lines. The baseband unit can include aplurality of baseband sub-units, wherein each baseband sub-unit caninclude a digital to analog converter (DAC) and an analog to digitalconverter (ADC). The RF unit can include a plurality of RF sub-units,wherein each RF unit can include a transmitter (TX) and a receiver (RX).Each set of inter-unit lines can connect a baseband sub-unit and acorresponding RF sub-unit. Moreover, each baseband sub-unit and itscorresponding RF sub-unit can form a processing section. Notably, a DACand a TX of one processing section and an RX and an ADC of anotherprocessing section can use the same set of inter-unit lines tocommunicate. This inter-unit line configuration minimizes the number oflines between the baseband and RF units.

This wireless communication system can further include a plurality ofintra-unit lines for connecting DACs and ADCs of different basebandsub-units and for connecting TXs and RXs of different RF sub-units.These intra-unit lines, along with the above-described sets ofinter-unit lines, can advantageously facilitate loopback testing. In oneembodiment to further facilitate loopback testing, the DACs and the RXscan have enabled/disabled output terminals. Note that each set ofinter-unit lines can include I/Q differential lines or other types oflines. Notably, in one embodiment, the baseband and RF units can beimplemented on different integrated circuits (ICs) and the plurality ofsets of inter-unit lines can be connected to pads of those ICs.

Another, more generalized, wireless communication system that reducesthe number of lines between baseband and RF units is provided. Thiswireless communication system can include a baseband unit, an RF unit,and a plurality of sets of inter-unit lines. The baseband unit caninclude a plurality of baseband sub-units and the RF unit can include aplurality of RF sub-units. Each set of inter-unit lines can connect abaseband sub-unit and a corresponding RF sub-unit. Moreover, eachbaseband sub-unit and its corresponding RF sub-unit can form aprocessing section. Advantageously, communication from a first basebandsub-unit to a first RF unit of a first processing section and from asecond RF sub-unit to a second baseband sub-unit of a second processingsection can share a set of inter-unit lines.

This generalized wireless communication system can further include aplurality of intra-unit lines for connecting components of differentbaseband sub-units and for connecting components of different RFsub-units. In one embodiment, certain components of each basebandsub-unit and RF sub-unit can have enabled/disabled output terminals tocoordinate sharing of the inter-unit lines. Note that each set ofinter-unit lines can include I/Q differential lines or other types oflines. In one embodiment, the baseband and RF units can be implementedon different ICs and the plurality of sets of inter-unit lines can beconnected to pads of the first and second ICs.

A method of communicating in a wireless system having theabove-described configurations can include communicating from a firstbaseband sub-unit to a first RF unit of a first processing section andfrom a second RF sub-unit to a second baseband sub-unit of a secondprocessing section by sharing a common set of inter-unit lines. In otherwords, communicating from the first baseband sub-unit to the first RFunit of the first processing section and from the first RF sub-unit tothe first baseband sub-unit can be advantageously accomplished usinginter-unit lines of different processing sections. To provide thedesired loopback configuration, two sets of inter-unit lines, intra-unitlines within the baseband and RF units, and antenna lines of thetargeted processing section can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a portion of a prior art wirelesscommunication system.

FIG. 2 is a block diagram illustrating portion of an exemplary multipletransceiver wireless communication system.

FIG. 3 is a block diagram illustrating a portion of an exemplarymultiple transceiver wireless communication system configured to reducethe number of lines between baseband and RF units.

FIG. 4 is a block diagram illustrating an exemplary embodiment of aportion of a multiple transceiver wireless communication systemconfigured according to the specification.

FIG. 5 is a block diagram illustrating another exemplary embodiment of aportion of a multiple transceiver wireless communication systemconfigured according to the specification.

DETAILED DESCRIPTION

Many wireless communication systems include baseband and RF units whereeach baseband and RF unit includes a plurality of baseband and RFsub-units, respectively. It is advantageous to reduce the relativenumber of inter-unit lines used to couple a baseband sub-unit to an RFsub-unit because as the number of sub-units increase, so may the numberof coupling lines. As described above, reducing the relative amount ofthe inter-unit lines may help ease system design and reduce costs.

One method to reduce the number of inter-unit lines between a basebandunit and an RF unit configures those units to use the same lines tocarry both receive baseband analog signals and transmit baseband analogsignals. This is possible because, oftentimes in normal operation, thebaseband unit is either processing data to transmit or to receive, butgenerally not processing transmit and receive data simultaneously. Inone embodiment, a DAC and an RX may have outputs that may becontrollably enabled. The outputs of the DAC may be enabled whentransmitting RF signals and the outputs of the RX may be enabled whenreceiving RF signals. In some embodiments, configuration may beaccomplished by controlling tri-state drives. In other embodiments,switches may selectively couple the active output to the inter-unitline.

FIG. 3 illustrates a portion of an exemplary multiple transceiverwireless communication system 300 configured to reduce the number oflines between a baseband unit 301 and an RF unit 311. In system 300,baseband unit 301 and RF unit 311 are each divided into three sub-units(i.e. A, B, and C). A first baseband sub-unit 301A includes a first DAC302A and a first ADC 303A, a second baseband sub-unit 301B includes asecond DAC 302B and a second ADC 303B, and a third baseband sub-unit301C includes a third DAC 302C and a third ADC 303C. Similarly, a firstRF sub-unit 311A includes a first TX 312A and a first RX 313A, a secondRF sub-unit 311B includes a second TX 312B and a second RX 313B, and athird RF sub-unit 311C includes a third TX 312C and a third RX 313C.

First DAC 301A is coupled to first TX 212A through a set of I/Qdifferential inter-unit lines 315. Notably, first RX 313A is coupled tofirst ADC 302A through the same set of I/Q differential inter-unit lines315. Second and third baseband sub-units are coupled to the second andthird RF sub-units, respectively, using similar sets of I/Q differentialinter-unit lines 315. Note that, for simplicity in FIG. 3 (andsubsequent figures), sets of I/Q differential lines have been reduced toa single line). Thus, in this embodiment, each line in the figure (otherthan the I/Q differential lines in and between baseband sub-unit 301Aand RF sub-unit 311A) represents I/Q differential lines. Therefore, inthis example, four I/Q differential lines couple each baseband sub-unitwith its corresponding RF sub-unit. Note that the black circlesrepresent full connections between the lines.

Advantageously, wireless communication system 300 of FIG. 3 hasrelatively few I/Q differential inter-unit lines between baseband unit301 and RF unit 311 because receive baseband analog signals and transmitbaseband analog signals may be carried on the same I/Q differentialinter-unit lines. In one embodiment, a DAC and a receiver may haveoutputs that may be controllably enabled/disabled during actualoperation. For example, to transmit an RF signal through first TX 312A,first DAC 302A may have its output enabled while the output of first RX313A is not enabled. Data from first DAC 302A may then be provided tofirst TX 312A. On the other hand, to receive an RF signal through firstRX 313A, the output of first RX 313A is enabled while the output offirst DAC 302A is not enabled. Data from first RX 313A may then beprovided to first ADC 303A.

Note that while wireless communication systems 200 and 300 (FIGS. 2 and3, respectively) are similarly configured with each system includingthree baseband sub-units and three RF sub-units, system 200 usestwenty-four I/Q differential inter-unit lines whereas system 300advantageously uses only twelve I/Q differential lines to couple thebaseband unit to the RF unit. One disadvantage, however, of system 300is that loopback testing of a selected RF unit cannot easily beconfigured.

Loopback testing, as described above, configures a loopback processingchain of elements within a baseband sub-unit and an RF sub-unit suchthat the elements may contemporaneously process test data, therebyenabling testing or calibration of one or more of the elements withinthe baseband sub-unit and the RF sub-unit. However, because wirelesscommunication system 300 cannot be so configured, loopback testingcannot be implemented. For example, referring to first baseband sub-unit301A and first RF sub-unit 311A, note that the output of first DAC 302Ais coupled to the input of first ADC 303A. Thus, first TX 312A and firstRX 313A may not be tested because the test data may pass substantiallybetween first DAC 302A and first ADC 303A, thereby bypassing first TX312A and first RX 313A. Because second and third baseband sub-units301B/301C and RF sub-units 311B/311C are similarly configured, thosesub-units may not be configured for loopback testing either.

FIG. 4 illustrates a portion of an exemplary wireless communicationsystem 400 configured to provide loopback testing. Wirelesscommunication system 400 includes a baseband unit 401 and an RF unit402, each of which is divided into three sub-units. A first basebandsub-unit 401A includes a first DAC 402A and a first ADC 403A, a secondbaseband sub-unit 401B includes a second DAC 402B and a second ADC 403B,and a third baseband sub-unit 4010 includes a third DAC 402C and a thirdADC 403C. A first RF sub-unit 411A includes a first TX 412A and a firstRX 413A, a second RF sub-unit 411B includes a second TX 412B and asecond RX 413B, and a third RF sub-unit 411C includes a third TX 412Cand a third RX 413C.

As described in further detail below, baseband sub-units 401A, 401B, and401C include I/Q differential intra-unit lines 416. RF sub-units 411A,411B, and 411C similarly include I/Q differential intra-unit lines 416and antenna lines 430 (note that antenna lines 430 are shown as beingon-chip, but could also be implemented off-chip). Using intra-unit lines416, first DAC 402A is coupled to second ADC 403B, second DAC 402B iscoupled to third ADC 403C, third DAC 402C is coupled to first ADC 403A,first TX 412A is coupled to second RX 413B, second TX 412B is coupled tothird RX 413C, and third TX 412C is coupled to first RX 413A. Antennalines 430 connect antenna 410A to TX 412A and RX 413A, antenna 410B toTX 412B and RX 413B, and antenna 410C to TX 412C and RX 413C.

In system 400, each baseband sub-unit can be characterized as having acorresponding RF sub-unit. For example, baseband sub-unit 401A has acorresponding RF sub-unit 411A, baseband sub-unit 401B has acorresponding RF sub-unit 411B, and baseband sub-unit 401C has acorresponding RF sub-unit 411C. Note that in other embodiments, basebandunit 401 and RF unit 402 may include two or more than three sub-units.As used herein, the term “processing section” refers to a basebandsub-unit and its corresponding RF unit. Thus, system 400 includes threeprocessing sections 420A, 420B, and 420C.

As described in further detail below, each processing section includes aset of I/Q differential inter-unit lines that connect a basebandsub-unit and its corresponding RF sub-unit. For example, processingsection 420A includes a set of I/Q differential inter-unit lines 415A.Similarly, processing section 420B includes a set of I/Q differentialinter-unit lines 415B, and processing section 420C includes a set of I/Qdifferential inter-unit lines 415C.

Notably, in contrast to wireless communication system 300 (FIG. 3), thetransmit baseband analog and the receive baseband analog signalsassociated with a specific processing section in wireless communicationsystem 400 are not carried on the same set of inter-unit lines. Forexample, first DAC 402A is coupled to first TX 412A using inter-unitlines 415A, whereas first RX 413A is coupled to first ADC 403A usinginter-unit lines 415C; second DAC 402B is coupled to second TX 412Busing inter-unit lines 415B, whereas second RX 413B is coupled to secondADC 403B using inter-unit lines 415A; and third DAC 402C is coupled tothird TX 413C using inter-unit lines 415C, whereas third RX 413C iscoupled to third ADC 403C using inter-unit lines 415B. This exemplaryarrangement of lines advantageously enables the configuration of one ormore loopback processing chains, as is described below in greaterdetail.

In one embodiment, the output terminals of the DACs and the RXs may becontrollably enabled to allow the transmit baseband analog signal andthe receive baseband analog signal to be carried on the same lines.During normal operation, wireless communication system 400 may beconfigured to transmit and receive RF signals in a manner similar towireless communication system 300 (FIG. 3). For example, to transmit anRF signal through first TX 402A, first DAC 402A may have its outputterminal enabled while the output terminal of second RX 413B is notenabled (noting that first DAC 402A and second RX 413B share the sameset of I/Q differential inter-unit lines). Data from first DAC 402A maythen be provided to first TX 412A. On the other hand, to receive an RFsignal through second RX 413B, the output terminal of second RX 413B isenabled while the output terminal of first DAC 402A is not enabled. Datafrom second RX 413B may then be provided to second ADC 403B.

Advantageously, wireless communication system 400 of FIG. 4 may beconfigured to enable loopback testing. In one embodiment, a basebandsub-unit may be coupled to an RF sub-unit and the elements within thosesub-units may form a loopback processing chain comprised of a DAC, atransmitter, a receiver and an ADC. All elements within the loopbackprocessing chain may function contemporaneously and process test datausing two sets of I/Q differential inter-unit lines, I/Q differentintra-unit lines extending across two or more sub-units, and the antennalines of the targeted processing section.

For example, first baseband sub-unit 401A and first RF sub-unit 411A(i.e. processing section 420A) may be configured for loopback testing.In this case, a loopback processing chain may be configured thatincludes first DAC 402A, first TX 412A, first RX 413A, and first ADC403A. First DAC 402A is coupled to first TX 412A (using a first set ofI/Q differential inter-unit lines). TX 412A is coupled to first RX 413Ausing antenna lines 430 of RF sub-unit 411A. Notably, RX 413A is coupledto first ADC 403A using I/Q differential intra-unit lines in RFsub-units 411A, 411B, and 411C, a second set of I/Q differentialinter-unit lines, and I/Q differential intra-unit lines in basebandsub-units 401A, 401B, and 401C (see dotted line 417 showing totalconnected path).

Loopback testing is possible within system 400 because all elementswithin a loopback processing chain may function contemporaneously andmay be coupled together in a manner that permits loopback testing. Thatis, in our example, the set of I/Q differential inter-unit linescoupling first DAC 402A to first TX 412A are separate from the set ofI/Q differential inter-unit lines coupling first RX 413A to first ADC403A. Therefore, the output of first DAC 402A and first RX 413A may bothbe enabled, thereby allowing the test data to be processed by theloopback processing chain. System 400 is configured such that the otherbaseband and RF sub-units shown in FIG. 4 may advantageously be testedin a similar manner.

Thus, wireless communication system 400 of FIG. 4 advantageouslyminimizes the number of inter-unit lines required to couple basebandunit 401 to RF unit 411. Relatively fewer inter-unit lines may reducethe cost of the IC package including system 400 because there arerelatively fewer pins required to connect to the inter-unit lines.Design costs may also be reduced because fewer inter-unit lines, such ashigh bandwidth I/Q differential lines, may have to be designed to couplethe baseband sub-units to the RF sub-units. The described lineconfiguration of system 400 also advantageously enables loopbacktesting. Thus, portions of system 400 may be tested or calibratedwithout the need to transmit or receive data to or from a secondwireless system.

In the exemplary wireless communication system of FIG. 4, the basebandsub-units include one DAC and one ADC. In other embodiments, a basebandsub-unit may include two or more DACs and two or more ADCs. Similarly,in other embodiments an RF sub-unit may include two or more transmittersand two or more receivers (i.e. two or more transceivers).

Exemplary wireless communication system 400 of FIG. 4 illustrates oneembodiment of a wireless communication system that may be configured toreduce the number of inter-unit lines while enabling loopback testing.In other embodiments, the elements in the RF unit and the baseband unitmay be coupled together in a different manner. For example, first DAC402A may be coupled to third ADC 403C and first TX 412A may be coupledto third RX 413C. In this case, a loopback processing chain may still beconfigured with DAC 402A, TX 412A, RX 413A and ADC 403A.

Although illustrative embodiments of the invention have been describedin detail herein with reference to the accompanying figures, it is to beunderstood that the invention is not limited to those preciseembodiments. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed. As such, many modificationsand variations will be apparent. For example, although FIG. 4illustrates DACs 402 being coupled to TXs 412 using fewer I/Qdifferential intra-unit lines compared to those used to couple RXs 413and ADCs 403, FIG. 5 illustrates a wireless communication system 500that reverses this configuration, i.e. DACs 402 being coupled to TXs 412using more I/Q differential intra-unit lines compared to those used tocouple RXs 413 and ADCs 403. Moreover, note that in other embodiments,the components of the baseband unit may be connected to the componentsof the RF unit with non-differential lines, such as single-ended linesor the like. In still other embodiments, the number of basebandsub-units may differ from the number of RF sub-units. Accordingly, it isintended that the scope of the invention be defined by the followingClaims and their equivalents.

The invention claimed is:
 1. A wireless communication system comprising:a baseband unit including a plurality of baseband sub-units; an RF unitincluding a plurality of RF sub-units, each RF sub-unit including anantenna; a plurality of sets of inter-unit lines, each set of inter-unitlines connecting a baseband sub-unit and a corresponding RF sub-unit,wherein each baseband sub-unit and its corresponding RF sub-unit form aprocessing section for providing baseband reception and transmission aswell as RF reception and transmission, and wherein communication from afirst baseband sub-unit to a first RF unit of a first processing sectionand from a second RF sub-unit to a second baseband sub-unit of a secondprocessing section share a set of inter-unit lines.
 2. The wirelesscommunication system of claim 1, further including a plurality ofintra-unit lines for connecting components of different basebandsub-units.
 3. The wireless communication system of claim 1, furtherincluding a plurality of intra-unit lines for connecting components ofdifferent RF sub-units.
 4. The wireless communication system of claim 1,wherein certain components of each baseband sub-unit and RF sub-unithave enabled/disabled output terminals to coordinate sharing of theinter-unit lines.
 5. The wireless communication system of claim 1,wherein each set of inter-unit lines includes I/Q differential lines. 6.The wireless communication system of claim 1, wherein the baseband unitis implemented on a first integrated circuit (IC) and the RF unit isimplemented on a second IC, and wherein the plurality of sets ofinter-unit lines are connected to pins of the first and second ICs.
 7. Amethod of communicating in a wireless system, the wireless systemincluding a baseband unit and an RF unit, the baseband unit including aplurality of baseband sub-units, the RF unit including a plurality of RFsub-units, each RF sub-unit including an antenna, each baseband sub-unitand its corresponding RF sub-unit forming a processing section forproviding baseband reception and transmission as well as RF receptionand transmission, the method comprising: communicating from a firstbaseband sub-unit to a first RF unit of a first processing section andfrom a second RF sub-unit to a second baseband sub-unit of a secondprocessing section by sharing a common set of inter-unit lines.
 8. Amethod of communicating in a wireless system, the wireless systemincluding a baseband unit and an RF unit, the baseband unit including aplurality of baseband sub-units, the RF unit including a plurality of RFsub-units, each RF sub-unit including an antenna, each baseband sub-unitand its corresponding RF sub-unit forming a processing section forproviding baseband reception and transmission as well as RF receptionand transmission, the method comprising: communicating from a firstbaseband sub-unit to a first RF unit of a first processing section andfrom the first RF sub-unit to the first baseband sub-unit usinginter-unit lines of different processing sections.
 9. A method ofproviding loopback testing in a wireless system, the wireless systemincluding a baseband unit and an RF unit, the baseband unit including aplurality of baseband sub-units, the RF unit including a plurality of RFsub-units, each RF sub-unit including an antenna, each baseband sub-unitand its corresponding RF sub-unit forming a processing section forproviding baseband reception and transmission as well as RF receptionand transmission, the method comprising: connecting a component of afirst baseband sub-unit to a component of a first RF sub-unit using afirst set of inter-unit lines; and connecting another component of thefirst RF sub-unit to another component of the first baseband sub-unitusing a second set of inter-unit lines, the first and second sets ofinter-unit lines corresponding to different processing sections.
 10. Themethod of claim 9, wherein the steps of connecting further include usingintra-unit lines and antenna lines to provide a loopback configuration.